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https://github.com/silverstripe/silverstripe-framework
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126 lines
4.6 KiB
Markdown
126 lines
4.6 KiB
Markdown
title: App Object and Kernel
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summary: Provides bootstrapping and entrypoint to the SilverStripe application
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# Kernel
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The [Kernel](api:SilverStripe\Core\Kernel) object provides a container for the various manifests, services, and components
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which a SilverStripe application must have available in order for requests to be executed.
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This can be accessed in user code via Injector
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```php
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use SilverStripe\Core\Kernel;
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use SilverStripe\Core\Injector\Injector;
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$kernel = Injector::inst()->get(Kernel::class);
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echo "Current environment: " . $kernel->getEnvironment();
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```
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## Kernel services
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Services accessible from this kernel include:
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* getContainer() -> Current [Injector](api:SilverStripe\Core\Injector\Injector) service
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* getThemeResourceLoader() -> [ThemeResourceLoader](api:SilverStripe\View\ThemeResourceLoader) Service for loading of discovered templates.
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Also used to contain nested theme sets such as the `$default` set for all root module /templates folders.
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* getEnvironment() -> String value for the current environment. One of 'dev', 'live' or 'test'
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Several meta-services are also available from Kernel (which are themselves containers for
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other core services) but are not commonly accessed directly:
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* getClassLoader() -> [ClassLoader](api:SilverStripe\Core\Manifest\ClassLoader) service which handles the class manifest
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* getModuleLoader() -> [Manifest](api:SilverStripe\Core\Manifest) service which handles module registration
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* getConfigLoader() -> [ConfigLoader](api:SilverStripe\Core\Config\ConfigLoader) Service which assists with nesting of [Config](api:SilverStripe\Core\Config\Config) instances
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* getInjectorLoader() -> [InjectorLoader](api:SilverStripe\Core\Injector\InjectorLoader) Service which assists with nesting of [Injector](api:SilverStripe\Core\Injector\Injector) instances
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## Kernel nesting
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As with Config and Injector the Kernel can be nested to safely modify global application state,
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and subsequently restore state. Unlike those classes, however, there is no `::unnest()`. Instead
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you should call `->activate()` on the kernel instance you would like to unnest to.
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```php
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$oldKernel = Injector::inst()->get(Kernel::class);
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try {
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// Injector::inst() / Config::inst() are automatically updated to the new kernel
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$newKernel = $oldKernel->nest();
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Config::modify()->set(Director::class, 'alternate_base_url', '/myurl');
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}
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finally {
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// Any changes to config (or other application state) have now been reverted
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$oldKernel->activate();
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}
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```
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# Application
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An application represents a basic execution controller for the top level application entry point.
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The role of the application is to:
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- Control bootstrapping of a provided kernel instance
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- Handle errors raised from an application
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- Direct requests to the request handler, and return a valid response
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## HTTPApplication
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The HTTPApplication provides a specialised application implementation for handling HTTP Requests.
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This class provides basic support for HTTP Middleware, such as [ErrorControlChainMiddleware](api:SilverStripe\Core\Startup\ErrorControlChainMiddleware).
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The `index.php` file in your project root contains the default application implementation.
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You can customise it as required.
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```php
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use SilverStripe\Control\HTTPApplication;
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use SilverStripe\Control\HTTPRequestBuilder;
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use SilverStripe\Core\CoreKernel;
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use SilverStripe\Core\Startup\ErrorControlChainMiddleware;
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require __DIR__ . '/vendor/autoload.php';
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// Build request and detect flush
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$request = HTTPRequestBuilder::createFromEnvironment();
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// Default application
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$kernel = new CoreKernel(BASE_PATH);
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$app = new HTTPApplication($kernel);
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$app->addMiddleware(new ErrorControlChainMiddleware($app));
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$response = $app->handle($request);
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$response->output();
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```
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## Custom application actions
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If it's necessary to boot a SilverStripe kernel and application, but not do any
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request processing, you can use the Application::execute() method to invoke a custom
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application entry point.
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This may be necessary if using SilverStripe code within the context of a non-SilverStripe
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application.
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For example, the below will setup a request, session, and current controller,
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but will leave the application in a "ready" state without performing any
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routing.
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```php
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$request = CLIRequestBuilder::createFromEnvironment();
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$kernel = new TestKernel(BASE_PATH);
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$app = new HTTPApplication($kernel);
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$app->execute($request, function (HTTPRequest $request) {
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// Start session and execute
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$request->getSession()->init();
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// Set dummy controller
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$controller = Controller::create();
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$controller->setRequest($request);
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$controller->pushCurrent();
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$controller->doInit();
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}, true);
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```
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